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  • Search dir using wildcard string, return filename, and loop.

    - by Charlie Murphy
    Hello all, I'm having some problems, and looking for some help. I'm trying to create a photo gallery in javascript, that will be able to 'update' it's self automatically. I need to be able to search a directory, and grab a file with a specific prefix. I need to output the followng HTML code: <li><a href="images/resize_FILENAME.ext"><img src="images/thumb_FILENAME.ext"></a></li> The 'resize_' and 'thumb_' use a timestamp to identify, so they have the same ending, just a different prefix. So, for example, if I search the directory for an image with a prefix of 'resize_', I need to insert that into the a tag, and then remove the '_resize' prefix, and add the '_thumb' prefix for the img tag. I then need to be able to do that for each image in the directory. Any help would be greatly appreciated. Oh, I should add: I'm assuming php would be easiest for this, but if an alternative exists that would work too. I'm also using jQuery if javascript would be better.

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  • Where should I put the code for a Django admin action for a third party app?

    - by charlie
    Hi, I'm new to Django. I am writing my own administrative action for a third party app/model, similar to this: http://mnjournal.com/post/2009/jul/10/adding-django-admin-actions-contrib-apps/ It's a simple snippet of code. I'm just wondering where people suggest that I put it. I don't want to put in the third party app because I might need to update to a newer version at some point. Thanks.

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  • Why does this Haskell code produce the "infinite type" error?

    - by Charlie Flowers
    I am new to Haskell and facing a "cannot construct infinite type" error that I cannot make sense of. In fact, beyond that, I have not been able to find a good explanation of what this error even means, so if you could go beyond my basic question and explain the "infinite type" error, I'd really appreciate it. Here's the code: intersperse :: a -> [[a]] -> [a] -- intersperse '*' ["foo","bar","baz","quux"] -- should produce the following: -- "foo*bar*baz*quux" -- intersperse -99 [ [1,2,3],[4,5,6],[7,8,9]] -- should produce the following: -- [1,2,3,-99,4,5,6,-99,7,8,9] intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:y:xs) = x:s:y:intersperse s xs And here's the error trying to load it into the interpreter: Prelude :load ./chapter.3.ending.real.world.haskell.exercises.hs [1 of 1] Compiling Main ( chapter.3.ending.real.world.haskell.exercises.hs, interpreted ) chapter.3.ending.real.world.haskell.exercises.hs:147:0: Occurs check: cannot construct the infinite type: a = [a] When generalising the type(s) for `intersperse' Failed, modules loaded: none. Thanks. EDIT: Thanks to the responses, I have corrected the code and I also have a general guideline for dealing with the "infinite type" error in Haskell: Corrected code intersperse _ [] = [] intersperse _ [x] = x intersperse s (x:xs) = x ++ s:intersperse s xs What the problem was: My type signature states that the second parameter to intersperse is a list of lists. Therefore, when I pattern matched against "s (x:y:xs)", x and y became lists. And yet I was treating x and y as elements, not lists. Guideline for dealing with the "infinite type" error: Most of the time, when you get this error, you have forgotten the types of the various variables you're dealing with, and you have attempted to use a variable as if it were some other type than what it is. Look carefully at what type everything is versus how you're using it, and this will usually uncover the problem.

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  • Fluent / NHibernate Collections of the same class

    - by Charlie Brown
    I am new to NHibernate and I am having trouble mapping the following relationships within this class. public class Category : IAuditable { public virtual int Id { get; set; } public virtual string Name{ get; set; } public virtual Category ParentCategory { get; set; } public virtual IList<Category> SubCategories { get; set; } public Category() { this.Name = string.Empty; this.SubCategories = new List<Category>(); } } Class Maps (although, these are practically guesses) public class CategoryMap : ClassMap<Category> { public CategoryMap() { Id(x => x.Id); Map(x => x.Name); References(x => x.ParentCategory) .Nullable() .Not.LazyLoad(); HasMany(x => x.SubCategories) .Cascade.All(); } } Each Category may have a parent category, some Categories have many subCategories, etc, etc I can get the Category to Save correctly (correct subcategories and parent category fk exist in the database) but when loading, it returns itself as the parent category. I am using Fluent for the class mapping, but if someone could point me in the right direction for just plain NHibernate that would work as well.

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  • how to load data and store the data from a file using numpy

    - by Charlie Epps
    I have the following file like this: 2 qid:1 1:0.32 2:0.50 3:0.78 4:0.02 10:0.90 5 qid:2 2:0.22 5:0.34 6:0.87 10:0.56 12:0.32 19:0.24 20:0.55 ... he structure is follwoing like that: output={} rel=2 qid=1 features={} # the feature list "1:0.32 2:0.50 3:0.78 4:0.02 10:0.90" output.append([rel,qid,features]) ... How can I write my python code to load the data, thanks

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  • Lazy loading? Better avoiding it?

    - by Charlie Pigarelli
    I just read about this design pattern: Lazy Load. And, since in the application i'm working on i have all the classes in one folder, i was wondering if this pattern could just make me avoiding the include() function for every class. I mean: It's nice to know that if i forgot to include a class, PHP, before falling into an error, trough an __autoload() function try to get it. But is it fine enough to just don't care about including classes and let PHP do it by your own every time? Or we should write __autoload() just in case it is needed?

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  • Is my way of doing threads in Android correct?

    - by Charlie
    Hi, I'm writing a live wallpaper, and I'm forking off two separate threads in my main wallpaper service. One updates, and the other draws. I was under the impression that once you call thread.start(), it took care of everything for you, but after some trial and error, it seems that if I want my update and draw threads to keep running, I have to manually keep calling their run() methods? In other words, instead of calling start() on both threads and forgetting, I have to manually set up a delayed handler event that calls thread.run() on both the update and draw threads every 16 milliseconds. Is this the correct way of having a long running thread? Also, to kill threads, I'm just setting them to be daemons, then nulling them out. Is this method ok? Most examples I see use some sort of join() / interrupt() in a while loop...I don't understand that one...

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  • Static methods requiring var

    - by Charlie Pigarelli
    Ok, i'm stuck on this, why don't i get what i need? class config { private $config; # Load configurations public function __construct() { loadConfig('site'); // load a file with $cf in it loadConfig('database'); // load another file with $cf in it $this->config = $cf; // $cf is an array unset($cf); } # Get a configuration public static function get($tag, $name) { return $this->config[$tag][$name]; } } I'm getting this: Fatal error: Using $this when not in object context in [this file] on line 22 [return $this->config[$tag][$name];] And i need to call the method in this way: config::get()...

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  • Is there a way to create my own "push pins" for a image without using Google Maps API?

    - by Charlie
    I am interested in working with friends via the internet on a fantasy world map. One of the things I want to do is host an image of the map online and allow us to insert push pins into the image that would then be associated with infoboxes. I don't want to resort to using the Google Map APIs mainly because this is something I want to just share among friends and not publicly. Terms of usage for the APIs state we would need to make the implementation available for everyone. This seems simple enough yet I've no idea how to do this. I looked into image maps, but that requires constant updates to the html markup itself. I just want to insert/delete/edit pushpins and infoboxes on the image and through our site itself. Can someone help me get started?

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  • Error comparing hash to hashed mysql password (output values are equal)

    - by Charlie
    Im trying to compare a hashed password value in a mysql database with the hashed value of an inputted password from a login form. However, when I compare the two values it says they aren't equal. I removed the salt to simply, and then tested what the outputs were and got the same values $password1 = $_POST['password']; $hash = hash('sha256', $password1); ...connect to database, etc... $query = "SELECT * FROM users WHERE username = '$username1'"; $result = mysql_query($query); $userData = mysql_fetch_array($result); if($hash != $userData['password']) //incorrect password { echo $hash."|".$userData['password']; die(); } ...other code... Sample output: 7816ee6a140526f02289471d87a7c4f9602d55c38303a0ba62dcd747a1f50361| 7816ee6a140526f02289471d87a7c4f9602d55c38303a0ba62dcd747a1f50361 Any thoughts?

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  • Find record whose field 'name' not contained within any other record

    - by charlie
    I have a model Foo with a String bar and a String name. Some records' bar contain the name of other records in them. This is intentional. I want to find the "root Foo" records - that is, the ones where their name do not appear in the bar records of any other Foo records. Example: Foo id: 1 name: 'foo1' bar: 'something something' id: 2 name: 'foo2' bar: 'foo1 something' id: 3 name: 'foo3' bar: 'foo1, foo4' My method root_foos would return foo2 and foo3 since their names do not appear in any bar string. edit: I don't want to use a relation or foreign key here - just this method.

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  • Quick and Dirty Backups with rsync

    It's not always the best tool for the job, but if you need to get a backup into the cloud quickly and easily, rsync might do the trick. Charlie Schluting steps you through how to build a script to do just that.

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  • Ma este Oracle Data Mining újdonságok webcast!

    - by Fekete Zoltán
    2010. május 12-én szerdán 18 órakor a böngészonkkel kapcsolódva a következo roppant érdekes eloadást hallgathatjuk meg az Oracle BIWA keretében: BIWA SIG TechCast Series - May 12 - Data Mining Made Easy, az eloadó Charlie Berger, az Oracle adatbányászati vezetoje. Könnyen elvégezheto adatbányászat! Az Oracle Data Miner 11g Release 2 új "Work flow" grafikus felületének bevezetése. Csatlakozni az Oracle BIWA-hoz a ezen a linken ingyenesen lehet. Itt találhatjuk meg, hogyan lehet meghallgatni ezt a konferenciát: www.oraclebiwa.org

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  • Harris Corporation Streamlines Manufacturing Assembly Operations with AutoVue

    - by Pam Petropoulos
    "AutoVue is a critical component to our business process; we can’t live without it.” – Charlie Davies, Principal ECAE Applications Engineer, Harris Corporation. Read how Harris Corporation, an international communications and information technology company in the high tech space, is using AutoVue to streamline their manufacturing assembly operations, enhance design reviews and improve communication of engineering changes. Click here to read the complete story.

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  • Oracle Service Bus Customer Panel - Choice Hotel's Deployment Description at OpenWorld

    - by Bruce Tierney
    Choice Hotels shared their Oracle Service Bus deployment during the recent Customer Panel on Oracle Service Bus.  Charlie Taylor of Choice provides an excellent in-depth description of architectural guidelines including project naming and project structure.  Below is a screenshot from the session highlighting the flow from proxy service to business service, transformation, orchestration and more: For more information about Oracle OpenWorld SOA & BPM Session, please see the Focus on SOA and BPM document 

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  • Apple publie une mise à jour de sécurité qui colmate la faille mise à jour lors du Pwn2Own 2010

    Apple a publié une mise à jour de sécurité pour Mac OS X Leopard et Mac OS X Snow Leopard, que ce soit la version normale ou la version Serveur. Cette mise à jour de sécurité colmate la faille que Charlie Miller avait mis à jour lors du Pwn2own 2010 qui s'était tenu fin mars. Voir http://support.apple.com/kb/HT4131 pour plus d'information sur la mise à jour sécurité 2010-003 Voir également Jusqu'ici, aucun navigateur ne résiste aux attaques des experts en séc...

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  • Silverlight Cream for April 29, 2010 -- #851

    - by Dave Campbell
    In this Issue: Carlos Figueira(-2-), Subodh Pushpak, Gergely Orosz, John Papa, Mike Snow(-2-), Rishi, Tim Heuer, Stefan Olson, and David Anson. Shoutouts: Josh Holmes blogged about a cool app the City of Miami has up: Miami 311: Built on Windows Azure Gergely Orosz reports on the state of a bug he found pre SL4: Silverlight 4 still displays large elements incorrectly Laura Foy and Charlie Kindel discuss WP7 on Channel 9: Windows Phone 7 Developer Tools Refresh Announced Charlie Kindel has an announcement, good instructions, and what's new notes on the Windows Phone Developer Tools CTP Refresh! Tim Heuer mentioned the workaround for this in his post (below), but I thought you might like to read Brandon Watson's debrief of what it's all about: Signed Assemblies Bug in the Windows Phone Tools CTP Refresh Laurent Bugnion posted about interrelations between versions of Blend and WP7 code... read it closely: Be careful when installing the Blend Windows Phone 7 Add-In From SilverlightCream.com: Consuming REST/POX services in Silverlight 4 Carlos Figueira has a pair of posts up about consuming services in Silverlight 4. This first one is about consuming REST/POX services. He provides a Service Contract that can be used with either and the full project code is available as well. Consuming REST/JSON services in Silverlight 4 In the second post, Carlos Figueira provides the code to allow WCF and Silverlight 4 to consume strongly-typed REST/JSON... and again, all the code is available. Silverlight and WCF caching Subodh Pushpak has a post up discussing caching in WCF, and has code demonstrating turning caching on at run-time. Detecting Silverlight Version Installed Gergely Orosz said it right when he said "Detecting the Silverlight version installed on a client machine isn’t entirely straightforward." ... and after reading this post, if you take the link to his ScottLogic blog, you'll get a full break-out of how it's done. Silverlight TV 22: Tim Heuer on Extending the SMF It's Thursday, and that means Silverlight TV! ... this week, John Papa has on Tim Heuer who has always been out there pushing media... and he's talking about SMF or Silverlight Media Framework for the uninitiated, and also extending it. Silverlight Tip of the Day #7 – Localized Resources Mike Snow has Tip Number 7 up and it's about localization... good end-to-end discussion and demonstration. Just thought I should use that to prove to my daughter that the tatoo she had put on the back of her neck actually reads "Eat More Broccoli" :) Silverlight Tip of the Day #8 – Detecting Alt, Shift, Control, Window & Apple Keys Combinations I just realized Mike Snow's site logo reads "Silverlight Tips of the Day" (bolding mine) ... that answers why I'm seeing more than one -- sorry Mike, couldn't pass it up :) ... Mike's second tip today and number 8 in the series is on detecting all the mouse button and ctl/alt/shift combinations in Silverlight. nRoute: More Wholesomeness, with SL 4 and .NET 4.0 Rishi has a post up announcing a new nRoute release for Silverlight 4 and .NET 4.0 He's tweaked the code to take advantages of enhancements in the new platforms, so check it out. Windows Phone 7 Developer Tools April 2010 Refresh Booya... Tim Heuer announced the release of the next drop in the WP7 tools ... dang wish I was at home today :) ... be sure to read the post for info such as the notes about Authenticode Assemblies and the release notes. Updates to Silverlight Multi-binding support Stefan Olson points up a SL4 change to Multi-binding support that he had previously blogged about. He shows the previous non-working example, and what you have to do to make it work now. Using XAML to create a custom wallpaper image for your mobile device David Anson has a solution for those pesky lost devices, and let me go on the record right now saying if anyone finds a WP7 phone laying around, just call me, it's mine :) [think that'd work??] ... ok, David's solution is a WPF app "MobileDeviceHomeScreenMaker" that you get the info set and it produces a png you then put on your device. But seriously about that lost phone... Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Correlate GROUP BY and LEFT JOIN on multiple criteria to show latest record?

    - by Sunbird
    In a simple stock management database, quantity of new stock is added and shipped until quantity reaches zero. Each stock movement is assigned a reference, only the latest reference is used. In the example provided, the latest references are never shown, the stock ID's 1,4 should have references charlie, foxtrot respectively, but instead show alpha, delta. How can a GROUP BY and LEFT JOIN on multiple criteria be correlated to show the latest record? http://sqlfiddle.com/#!2/6bf37/107 CREATE TABLE stock ( id tinyint PRIMARY KEY, quantity int, parent_id tinyint ); CREATE TABLE stock_reference ( id tinyint PRIMARY KEY, stock_id tinyint, stock_reference_type_id tinyint, reference varchar(50) ); CREATE TABLE stock_reference_type ( id tinyint PRIMARY KEY, name varchar(50) ); INSERT INTO stock VALUES (1, 10, 1), (2, -5, 1), (3, -5, 1), (4, 20, 4), (5, -10, 4), (6, -5, 4); INSERT INTO stock_reference VALUES (1, 1, 1, 'Alpha'), (2, 2, 1, 'Beta'), (3, 3, 1, 'Charlie'), (4, 4, 1, 'Delta'), (5, 5, 1, 'Echo'), (6, 6, 1, 'Foxtrot'); INSERT INTO stock_reference_type VALUES (1, 'Customer Reference'); SELECT stock.id, SUM(stock.quantity) as quantity, customer.reference FROM stock LEFT JOIN stock_reference AS customer ON stock.id = customer.stock_id AND stock_reference_type_id = 1 GROUP BY stock.parent_id

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  • BDD IS Different to TDD

    - by Liam McLennan
    One of this morning’s sessions at Alt.NET 2010 discussed BDD. Charlie Pool expressed the opinion, which I have heard many times, that BDD is just a description of TDD done properly. For me, the core principles of BDD are: expressing behaviour in terms that show the value to the system actors Expressing behaviours / scenarios in a format that clearly separates the context, the action and the observations. If we go back to Kent Beck’s TDD book neither of these elements are mentioned as being core to TDD. BDD is an evolution of TDD. It is a specialisation of TDD, but it is not the same as TDD. Discussing BDD, and building specialised tools for BDD, is valuable even though the difference between BDD and TDD is subtle. Further, the existence of BDD does not mean that TDD is obsolete or invalidated.

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  • International Radio Operators Alphabet in F# &amp; Silverlight &ndash; Part 1

    - by MarkPearl
    So I have been delving into F# more and more and thought the best way to learn the language is to write something useful. I have been meaning to get some more Silverlight knowledge (up to now I have mainly been doing WPF) so I came up with a really simple project that I can actually use at work. Simply put – I often get support calls from clients wanting new activation codes. One of our main app’s was written in VB6 and had its own “security” where it would require about a 45 character sequence for it to be activated. The catch being that each time you reopen the program it would require a different character sequence, which meant that when we activate clients systems we have to do it live! This involves us either referring them to a website, or reading the characters to them over the phone and since nobody in the office knows the IROA off by heart we would come up with some interesting words to represent characters… 9 times out of 10 the client would type in the wrong character and we would have to start all over again… with this app I am hoping to reduce the errors of reading characters over the phone by treating it like a ham radio. My “Silverlight” application will allow for the user to input a series of characters and the system will then generate the equivalent IROA words… very basic stuff e.g. Character Input – abc Words Generated – Alpha Bravo Charlie After listening to Anders Hejlsberg on Dot Net Rocks Show 541 he mentioned that he felt many applications could make use of F# but in an almost silo basis – meaning that you would write modules that leant themselves to Functional Programming in F# and then incorporate it into a solution where the front end may be in C# or where you would have some other sort of glue. I buy into this kind of approach, so in this project I will use F# to do my very intensive “Business Logic” and will use Silverlight/C# to do the front end. F# Business Layer I am no expert at this, so I am sure to get some feedback on way I could improve my algorithm. My approach was really simple. I would need a function that would convert a single character to a string – i.e. ‘A’ –> “Alpha” and then I would need a function that would take a string of characters, convert them into a sequence of characters, and then apply my converter to return a sequence of words… make sense? Lets start with the CharToString function let CharToString (element:char) = match element.ToString().ToLower() with | "1" -> "1" | "5" -> "5" | "9" -> "9" | "2" -> "2" | "6" -> "6" | "0" -> "0" | "3" -> "3" | "7" -> "7" | "4" -> "4" | "8" -> "8" | "a" -> "Alpha" | "b" -> "Bravo" | "c" -> "Charlie" | "d" -> "Delta" | "e" -> "Echo" | "f" -> "Foxtrot" | "g" -> "Golf" | "h" -> "Hotel" | "i" -> "India" | "j" -> "Juliet" | "k" -> "Kilo" | "l" -> "Lima" | "m" -> "Mike" | "n" -> "November" | "o" -> "Oscar" | "p" -> "Papa" | "q" -> "Quebec" | "r" -> "Romeo" | "s" -> "Sierra" | "t" -> "Tango" | "u" -> "Uniform" | "v" -> "Victor" | "w" -> "Whiskey" | "x" -> "XRay" | "y" -> "Yankee" | "z" -> "Zulu" | element -> "Unknown" Quite simple, an element is passed in, this element is them converted to a lowercase single character string and then matched up with the equivalent word. If by some chance a character is not recognized, “Unknown” will be returned… I know need a function that can take a string and can parse each character of the string and generate a new sequence with the converted words… let ConvertCharsToStrings (s:string) = s |> Seq.toArray |> Seq.map(fun elem -> CharToString(elem)) Here… the Seq.toArray converts the string to a sequence of characters. I then searched for some way to parse through every element in the sequence. Originally I tried Seq.iter, but I think my understanding of what iter does was incorrect. Eventually I found Seq.map, which applies a function to every element in a sequence and then creates a new collection with the adjusted processed element. It turned out to be exactly what I needed… To test that everything worked I created one more function that parsed through every element in a sequence and printed it. AT this point I realized the the Seq.iter would be ideal for this… So my testing code is below… let PrintStrings items = items |> Seq.iter(fun x -> Console.Write(x.ToString() + " ")) let newSeq = ConvertCharsToStrings("acdefg123") PrintStrings newSeq Console.ReadLine()   Pretty basic stuff I guess… I hope my approach was right? In Part 2 I will look into doing a simple Silverlight Frontend, referencing the projects together and deploying….

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  • LINQ und ArcObjects

    - by Marko Apfel
    LINQ und ArcObjects Motivation LINQ1 (language integrated query) ist eine Komponente des Microsoft .NET Frameworks seit der Version 3.5. Es erlaubt eine SQL-ähnliche Abfrage zu verschiedenen Datenquellen wie SQL, XML u.v.m. Wie SQL auch, bietet LINQ dazu eine deklarative Notation der Problemlösung - d.h. man muss nicht im Detail beschreiben wie eine Aufgabe, sondern was überhaupt zu lösen ist. Das befreit den Entwickler abfrageseitig von fehleranfälligen Iterator-Konstrukten. Ideal wäre es natürlich auf diese Möglichkeiten auch in der ArcObjects-Programmierung mit Features zugreifen zu können. Denkbar wäre dann folgendes Konstrukt: var largeFeatures = from feature in features where (feature.GetValue("SHAPE_Area").ToDouble() > 3000) select feature; bzw. dessen Äquivalent als Lambda-Expression: var largeFeatures = features.Where(feature => (feature.GetValue("SHAPE_Area").ToDouble() > 3000)); Dazu muss ein entsprechender Provider zu Verfügung stehen, der die entsprechende Iterator-Logik managt. Dies ist leichter als man auf den ersten Blick denkt - man muss nur die gewünschten Entitäten als IEnumerable<IFeature> liefern. (Anm.: nicht wundern - die Methoden GetValue() und ToDouble() habe ich nebenbei als Erweiterungsmethoden deklariert.) Im Hintergrund baut LINQ selbständig eine Zustandsmaschine (state machine)2 auf deren Ausführung verzögert ist (deferred execution)3 - d.h. dass erst beim tatsächlichen Anfordern von Entitäten (foreach, Count(), ToList(), ..) eine Instanziierung und Verarbeitung stattfindet, obwohl die Zuweisung schon an ganz anderer Stelle erfolgte. Insbesondere bei mehrfacher Iteration durch die Entitäten reibt man sich bei den ersten Debuggings verwundert die Augen wenn der Ausführungszeiger wie von Geisterhand wieder in die Iterator-Logik springt. Realisierung Eine ganz knappe Logik zum Konstruieren von IEnumerable<IFeature> lässt sich mittels Durchlaufen eines IFeatureCursor realisieren. Dazu werden die einzelnen Feature mit yield ausgegeben. Der einfachen Verwendung wegen, habe ich die Logik in eine Erweiterungsmethode GetFeatures() für IFeatureClass aufgenommen: public static IEnumerable GetFeatures(this IFeatureClass featureClass, IQueryFilter queryFilter, RecyclingPolicy policy) { IFeatureCursor featureCursor = featureClass.Search(queryFilter, RecyclingPolicy.Recycle == policy); IFeature feature; while (null != (feature = featureCursor.NextFeature())) { yield return feature; } //this is skipped in unit tests with cursor-mock if (Marshal.IsComObject(featureCursor)) { Marshal.ReleaseComObject(featureCursor); } } Damit kann man sich nun ganz einfach die IEnumerable<IFeature> erzeugen lassen: IEnumerable features = _featureClass.GetFeatures(RecyclingPolicy.DoNotRecycle); Etwas aufpassen muss man bei der Verwendung des "Recycling-Cursors". Nach einer verzögerten Ausführung darf im selben Kontext nicht erneut über die Features iteriert werden. In diesem Fall wird nämlich nur noch der Inhalt des letzten (recycelten) Features geliefert und alle Features sind innerhalb der Menge gleich. Kritisch würde daher das Konstrukt largeFeatures.ToList(). ForEach(feature => Debug.WriteLine(feature.OID)); weil ToList() schon einmal durch die Liste iteriert und der Cursor somit einmal durch die Features bewegt wurde. Die Erweiterungsmethode ForEach liefert dann immer dasselbe Feature. In derartigen Situationen darf also kein Cursor mit Recycling verwendet werden. Ein mehrfaches Ausführen von foreach ist hingegen kein Problem weil dafür jedes Mal die Zustandsmaschine neu instanziiert wird und somit der Cursor neu durchlaufen wird – das ist die oben schon erwähnte Magie. Ausblick Nun kann man auch einen Schritt weiter gehen und ganz eigene Implementierungen für die Schnittstelle IEnumerable<IFeature> in Angriff nehmen. Dazu müssen nur die Methode und das Property zum Zugriff auf den Enumerator ausprogrammiert werden. Im Enumerator selbst veranlasst man in der Reset()-Methode das erneute Ausführen der Suche – dazu übergibt man beispielsweise ein entsprechendes Delegate in den Konstruktur: new FeatureEnumerator( _featureClass, featureClass => featureClass.Search(_filter, isRecyclingCursor)); und ruft dieses beim Reset auf: public void Reset() {     _featureCursor = _resetCursor(_t); } Auf diese Art und Weise können Enumeratoren für völlig verschiedene Szenarien implementiert werden, die clientseitig restlos identisch nach obigen Schema verwendet werden. Damit verschmelzen Cursors, SelectionSets u.s.w. zu einer einzigen Materie und die Wiederverwendbarkeit von Code steigt immens. Obendrein lässt sich ein IEnumerable in automatisierten Unit-Tests sehr einfach mocken - ein großer Schritt in Richtung höherer Software-Qualität.4 Fazit Nichtsdestotrotz ist Vorsicht mit diesen Konstrukten in performance-relevante Abfragen geboten. Dadurch dass im Hintergrund eine Zustandsmaschine verwalten wird, entsteht einiges an Overhead dessen Verarbeitung zusätzliche Zeit kostet - ca. 20 bis 100 Prozent. Darüber hinaus ist auch das Arbeiten ohne Recycling schnell ein Performance-Gap. Allerdings ist deklarativer LINQ-Code viel eleganter, fehlerfreier und wartungsfreundlicher als das manuelle Iterieren, Vergleichen und Aufbauen einer Ergebnisliste. Der Code-Umfang verringert sich erfahrungsgemäß im Schnitt um 75 bis 90 Prozent! Dafür warte ich gerne ein paar Millisekunden länger. Wie so oft muss abgewogen werden zwischen Wartbarkeit und Performance - wobei für mich Wartbarkeit zunehmend an Priorität gewinnt. Zumeist ist sowieso nicht der Code sondern der Anwender die Bremse im Prozess. Demo-Quellcode support.esri.de   [1] Wikipedia: LINQ http://de.wikipedia.org/wiki/LINQ [2] Wikipedia: Zustandsmaschine http://de.wikipedia.org/wiki/Endlicher_Automat [3] Charlie Calverts Blog: LINQ and Deferred Execution http://blogs.msdn.com/b/charlie/archive/2007/12/09/deferred-execution.aspx [4] Clean Code Developer - gelber Grad/Automatisierte Unit Tests http://www.clean-code-developer.de/Gelber-Grad.ashx#Automatisierte_Unit_Tests_8

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